I ALWAYS go with the manufacturer's spec for derailleurs. If SRAM says 33, then 33 it is. I ALWAYS size chains on the bike. Formulas and counting links are a waste of time. If you want to use a 10-36 get the new derailleur that's designed for it. In the past I've used the small/small method as it gives you the longest (safest) chain length as long as all parts of the drivetrain are with the spec for the rear derailleur. Some of the new mtb drivetrains need slightly shorter chains so I use the recommended method from the manufacturer. In other words, RTFM and do what it says. Don't worry about over-extended derailleurs. Don't overthink chain installation.